In the production of xerographic paper, it is known to formulate paper with either of a chemical pulp or mechanical pulp. In general, chemical pulp is formed starting with wood chips which are subjected to chemical, heat, and pressure to separate the cellulose fibers from the wood to prepare the pulp. Since cellulose represents less than half of the weight of the wood, the yield is typically about 45% of the wood weight available to the paper manufacturer. Mechanical pulp can be prepared by the mechanical grinding of wood, resulting in about 90% of the wood weight converted to papermaking fiber. The grinding is done with refiners powered in part by hydroelectricity, and the heat of the steam produced during the grinding is utilized in the papermaking operation to dry the paper. Thus, production of chemical pulp requires approximately twice the number of trees compared to production of a like quantity of mechanical pulp. Accordingly, there is high demand for environmentally friendly paper predominantly or exclusively incorporating mechanical fibers.
However, as part of the xerographic process, paper passes through a fusing system, in which heat and/or pressure is applied to the paper in order to fix a toner to the sheet. The presence of heat can cause a moisture loss within fibers of the paper to the extent that the paper can contract. Uneven contraction of the paper fibers across the thickness (Z-direction) of the sheet can result in an undesirable curling of the paper
Problems can occur with excessive curling of the paper. For example, curling of the paper can affect performance of the paper in both a xerographic unit and subsequent paper handling devices. Thus, the curl should be maintained within predetermined acceptable limits.
In known papermaking processes, the curl can be maintained at predetermined limits by making adjustments to the papermaking machine. However, these adjustments can be time consuming, requiring substantial down time for printing units as components are adjusted. Adjustment can be required at any of the wet end, wires, ringers, dyers, calenders, and dry end of the equipment for even a single run. However, adjustment for curl of the formed paper per se, still does not satisfactorily address the end use of the manufactured paper as xerographic paper, which is subject to press heat. Manufacturers may use several methods to predict curl performance in xerographic systems, however, no consistent and satisfactory limits of curl have been established and repeatable achieved prior to the following disclosure.
Thus, there is a need to overcome these and other problems of the prior art and to provide a method and product including mechanical fiber to yield a xerographic paper having a predetermined curl properties.